The allergy related illnesses asthma and hayfever are the two most common conditions of the respiratory tract. Hayfever is triggered by an immune system response to proteins from outdoor allergens such as pollen and mold spores while asthma is usually caused by indoor allergens such as dust mites, animal fur and dander, and cockroaches and other pests.
Individuals With Allergies Have More Immunoglobulin E Antibodies
But why do some people get ill in response to these allergens while others do not have any reaction at all? This occurs because the immune system of individuals who do not have allergy related illnesses respond weakly or not all to these triggers. At the chemical level in the body, their immune systems produce mainly antibodies called immunoglobulin G (IgG) in response to these allergens.
Conversely, individuals that suffer from allergies produce large amounts of the antibody immunoglobulin E (IgE). It is this overproduction of IgE antibody in response to otherwise harmless allergens that cause allergic reactions and symptoms.
Overproduction of the antibody IgE leads to other events in the immune system that cause allergies. The primary interaction is that of IgE with white blood cells called mast cells. These cells have receptors on their surfaces that bind to IgE antibodies. Hence after the initial exposure to an allergen such as pollen, the mast cells will have large numbers of IgE attached to them.
On the next exposure to the allergen, the mast cells are instructed to release their granules to attack the invader. Mast cell granules contain histamine and other powerful enzymes and chemicals that lead to allergy symptoms such as a runny nose, sneezing, wheezing and difficulty breathing.
Factors That Cause Allergy Symptoms
On their own, IgE antibodies can only live for about a day circulating in the blood. However, once they attach to mast cells they can remain alive for several weeks. This means that an allergy-suffer will likely continue sneezing all through pollen season in the spring and an asthma sufferer may feel the effects of a dusty carpet for days after exposure.
Factors that determine whether an individual will have allergies include early exposure to environmental allergens or infectious disease and genetic factors. Heredity plays a key role in whether a person suffers from allergies. This is thought to be due to the inheritance of a particular class of gene called MHC. This gene can make a person more susceptible to allergies, but doesn’t mean that they will have allergies.
Source
- "IgE's Role in Allergic Asthma" Asthma and Allergy Foundation of America.
Disclaimer: The information contained in this article is for educational purposes only and should not be used for diagnosis or to guide treatment without the opinion of a health professional. Any reader who is concerned about his or her health should contact a doctor for advice.
Noreen Kassem - Noreen Kassem is a hospital doctor based in London, UK. She has extensive experience in clinical research and an undergraduate honors ...
